This proposed work is designed to test the hypothesis that control of food intake of animals fed a diet deficient in one of the key nutrients (e.g., essential amino acids) is mediated by certain neural sensitive areas (receptors) responding to metabolite levels in the central nervous system and/or elsewhere in a certain manner as to trigger the mechanisms for such control. We intend to monitor, in detail, the dietary patterns of animals in terms of changes in meal size and frequency using electronic recording balances so as to correlate meal patterns with changes in metabolic events induced by various treatments which include using normal intact or lesion-bearing animals in certain areas of the brain involved in the control of feedings and, infusing such animals with amino acids (isotopically labeled or unlabeled), other metabolites, drugs or neural humors via chronically implanted cannulas in the brain, blood vessels (carotid artery, jugular or portal vein) or other areas in the animal body. Also key metabolites in the blood plasma, brain and other tissues will be analyzed to correlate their levels with dietary patterns. Areas of the brain to be examined include hypothalamic and extra-hypothalamic neural areas such as the anterior prepyriform cortex, the medial amygdala, the lateral septum, the dorsal lateral hippocampus, as well as the midbrain. The results from these studies should help to elucidate the location and the manner through which the neural sensitive areas mediate the mechanisms involved in the control of feeding. BIBLIOGRAPHIC REFERENCES: Stickney, G.G., P.M.B. Leung, Q.R. Rogers, S. Lepkovsky and P. Schmidt. The effect of total gastrectomy on free feeding patterns in rats. Federation Proceedings 35:520 (Abstract Number 1734), 1976. Leung, P.M.B. and B.A. Horwitz. Feeding patterns of rats in response to changes in energy demand. Federation Proceedings 35:520 (Abstract Number 1733), 1976.